The Parallel Worlds Proof
by amtrak12
Summary: aka Brilliant Collision - A familiar blue box lands in Leonard and Sheldon's living room. Why is it there? Are the Doctor and Donna now trapped forever in the wrong universe? - Epilogue now up!
1. Prelude

**The Parallel Worlds Proof**

_A Big Bang Theory/Doctor Who crossover_

**Spoilers:** Through _The Gorilla Experiment_ for BBT. Vague series 4 spoilers for Doctor Who.

**Author's Note:** This is something I tried to write last summer, but it didn't flow right and I wasn't sure where I was going with it. Decided to revisit this idea a couple of weeks ago and managed to clean up the dialogue, fix the flow, and (accidentally) add plot. So what started last year as an excuse to have Sheldon and the Doctor argue, turned into, well...this. It's still in progress, but I've got enough done that I feel comfortable posting some chapters. Just a short prelude for now. Chapter 1 will be up tomorrow.

**Prelude**

_Click, click, tik, tik, click._

Howard's head jerked up. He looked around confused. _'What the hell was that?'_ He heard the odd clicking noise again, this time farther to his left. He stood up and began to look around and under the tables. It sounded like an insect. An incredibly big insect. Howard crept forward to check the other side of the bookcase. Something black skittered across his peripheral vision, and he spun around. Nothing. He couldn't see anything out of place.

"Howard!!" called Leonard from down the hall. A few seconds later, he and Raj poked their heads through the doorway.

"Dude, what's taking you so long? We've got a killer robot to build!" Raj demanded.

"Right," Howard shook his head to clear it. "Right, just let me grab the servos." He grabbed a bag from his work bench and turned to go. He flipped out the lights as he followed Leonard and Raj out.

Tucked away, deep within the shadows, sat a rather large beetle-like creature. It made no movement. Simply stood and watched and waited. A second bag sat on top of the work bench, forgotten. No one ever returned for it. Finally, the beetle turned and slipped away amongst a flurry of clicks. It's job was done.

***~~***


	2. Ch 1: The Big Blue Box

**The Parallel Worlds Proof**

**A/N:** First full chapter! This is also the only chapter that almost has a cliff-hanger/tease at the end. Almost. The rest of the chapters just kind of blend together. Chapter 2 will be up tomorrow! In the meantime, I hope you enjoy. [Note: We skip forward several months between the prelude and here. Everything from this point on takes place at some point in season 3.]

**Chapter 1: The Big Blue Box**

Penny was more than ready to be home. The restaurant had been swamped most of the night, and she felt sore, exhausted, and very crabby. She heaved a sigh of relief as she reached the end of the stairs leading to her floor. When she reached for her keys, however, her moment of relief was cut short by this horrible grinding, screeching noise that seemed to crescendo even as it faded in and out. Penny turned around and glared at her boyfriend's apartment door. It was coming from inside. '_What stupid game or experiment are they doing now?'_ She wondered as she stomped over and banged on the door. No answer. The noise had stopped, but Penny was pissed and wanted to make sure the guys knew she was pissed so she threw open the door and barged in.

"Guys, how many times have I told you to keep the noise down?!" No one looked up from the center of the room to acknowledge her presence. Leonard, Sheldon, Howard, and Raj were all seated with headphones on, laptops in front of them, and shouting commands at each other. Obviously, they were engrossed in whatever MMO they were playing. Penny rolled her eyes and shook her head. That's when she saw it. This large looming blue box in the back of the room near the window. Penny focused her attention on it and took a step towards it. The words 'POLICE Public Call BOX' were written across the top. The windows and words were back-lit with a low yellow light. What the hell did the guys buy now? And how the hell did they get it upstairs? The thing was massive. Well okay, it was really about the size of a normal telephone box, but it seemed to be made from solid wood and was definitely too heavy for Leonard and them to have moved.

Seeing as the boys still had not noticed her, Penny crossed to the back of the room for a closer inspection. There were doors on the side facing out into the room. They were partially blocked in by the side table next to the couch. Penny gave an experimental push on one of the doors. It swung in a bit so it wasn't locked. Penny couldn't think of why it might have been locked. Of course, she's still confused as to why it's there at all. Maybe it was some sort of panic room that Sheldon bought. Penny smiled at that. She bet it would be easy to 'accidentally' lock Sheldon inside. Wait, except it probably had a way to unlock the doors from the inside. Penny opened the closest door and squeezed inside to check. She promptly squeaked in surprise.

Whatever she was expecting to see inside the box, it was most definitely NOT a brown room that looked as big as her entire apartment with two people arguing in the center. Upon hearing her squeak, the two people whirled around to stare at her. The woman turned back to the man and smacked him on the arm. "I said you got the coordinates wrong!" Even in her shock, Penny recognized her accent as British.

"Oi!" The man yelled back indignant. "This could still be the Giligna Plains. Tell me, what planet are we on?" This last part was addressed to Penny, but she had had enough. She immediately spun around, wrenched open the door, and squeezed back out into the apartment.

_'Holy crap on a cracker'_ Penny thought. "Leonard!" No answer. "LEONARD!" she shouted marching over to him and pulling off his headphones.

"Hey, what the ..! Oh Penny. Hi! Can you just hold on one minute? We're trying to grab control of this castle."

"No I cannot hold on!! Have you seen that large blue box over there?!! What the hell is it?! And why are there two British people inside asking what planet we're on???!" By this point, the other three guys had removed their headphones too, and Penny was on the receiving end of four very blank looks. Leonard spoke first.

"Blue box? Penny, what are you talking about?" He looked behind her in the direction she was pointing.

"What the frak?" said Howard, as he spotted it too. "Where did that come from?"

"I have no idea, but it looks vaguely familiar." said Leonard.

"No," Sheldon said in a low, awed whisper. Everyone looked at him.

"Do you know what that is?" asked Leonard.

"It's the Tardis" Sheldon answered still awed.

***~~***


	3. Ch 2: Meet the Doctor

**The Parallel Worlds Proof**

**A/N: **The second and third installments are really part of the same chapter. Chapter 2 was getting _really_ long so I just split it about half-way. I've got 2 more installments completed, but I've hit some bumps in the chapter after that. I should have it worked in time so the story won't be delayed in posting, but just in case, I thought I'd give you guys a heads-up.

**Disclaimer:** I keep forgetting these. I do not own anything from Big Bang Theory or Doctor Who! Just some DVD sets that I watch far too much. :P

**Chapter 2 - Meet the Doctor**

_ "Do you know what that is?" asked Leonard._

_ "It's the Tardis" Sheldon answered still awed._

"The tardis?" Penny repeated. "Is this another one of those stupid movie props, you bought off of Ebay?" She glared back at Leonard.

"Do not look at me, I learned my lesson with the time machine," Leonard insisted.

"Well someone brought it up here. How did you guys not know it was there?"

Sheldon had stood up from the couch and walked over to it by this point. "The Tardis must have materialized here. We must not have heard it over our game." Raj leaned over and whispered to Howard.

"Raj is right. The Tardis couldn't have actually materialized here in your apartment. It's not _real_. Besides the materialization sequence is incredibly loud, there's no way we would have not heard it."

Penny raised an eyebrow. "Really? Do you know how many times I've mentioned sex or taking off my clothes while you four were absorbed in something?"

Howard stared up at her with his mouth hanging open. "Say what?" Penny rolled her eyes.

"Okay, so it's obviously not the actual Tardis, but we still have an issue with it appearing here without any of us noticing" Leonard stated.

"Well based off of Penny's statement, I guess someone could have brought it in and dropped it there while we were playing WoW," Howard suggested.

Leonard shook his head. "That phone box is too large to fit through the door. They would have had to carry it up in pieces and put it together inside the apartment. It would have taken hours. We're oblivious, but we're not THAT oblivious."

Sheldon, gingerly touching the wooden door frame as if it was something sacred, called out, "I'm telling you, this is the actual Tardis. It's the only logical explanation."

"How is that the logical explanation?" Leonard cried incredulously.

"What is a tardis??" Penny asked.

"It's a transdimensional ship that travels through time and space," Leonard explained.

"Yes and it only exists in the British sci-fi show _Doctor Who,_" Howard clarified.

"Excuse me," Sheldon said as he turned around to face Howard, "are you aware of how many parallel worlds there are in existence? It is entirely possible that in one of them what we call the fictional show _Doctor Who_ exists as reality."

"Are you listening to yourself?! How could a TV show exist as reality in another universe?" Howard argued, standing up now from the couch too.

"Hang on, hang on!" Leonard interrupted. "Penny, did you say something about two British people being inside the box?"

"Yeah, the woman smacked the guy when they saw me, and the man asked me what planet we were on."

Sheldon looked over at Penny with keen interest. "What did they look like?"

Penny shrugged in confusion. "I don't know, I was a bit more shocked over the fact that they were there and standing inside a room that was way too big for that box." She noticed all the guys' eyes widen at this. "What?"

"Oh my god," said Howard.

Raj's mouth hung open in stunned silence.

"Which one do you think it is?" Leonard asked awed.

"Hard to say without more information," Sheldon replied. "Penny, what did the room look like? What color was the woman's hair? What was the man wearing?"

Penny glanced around at them confused. "I don't know. What are you guys all shocked by?"

"Was the room white or gold and brown?" Sheldon clarified.

"Why don't you just go in and look for yourself?" Penny asked.

Howard cut in. "Hang on, if there's someone inside, why haven't they come out yet?"

"Howard's got a point. The Doctor is never one for hanging back inside the Tardis whenever they land somewhere new."

"You don't think someone stole the Tardis, do you?" Leonard asked. Howard's eyes widened again.

"Like who, the Master or someone?" Howard shuddered. "Oooo, that would be terrifying. Awesome. But terrifying."

Penny had enough. "Oh for Pete's sake." She marched over to the Tardis doors again and slipped back inside. The man was now buried underneath the grating by the central console with wires and cables going every which way, and the woman was glaring down at him, still berating him.

"Well obviously not, if we can't dematerialize. We can't even tell where we are right now!"

"You know, Donna, this would go a lot faster if you weren't shouting so much. I need to concentrate!" The woman, Donna apparently, rolled her eyes and opened her mouth for a retort, but Penny cut in.

"Excuse me! But we were wondering who you are and what the hell you're doing parked in our living room?" The woman jumped almost at the same moment Penny heard a loud thud echo from somewhere.

"Who the hell is that?" cried the man as he scrambled up out of the grating and rubbing the back of his head.

"The same woman who got in earlier," Donna replied. "I thought you said no one could get in here. Not even the hoards of whats-his-name ."

"The assembled hoards of Genghis Khan . And they can't. Which must mean the Tardis defenses are down. Oh that is NOT good." The man raced to other side of the center control column and started punching buttons and looking at a screen. "NNNGGHHHH! Still can't get anything." Frustrated, he ran his hands through his hair, messing it up further than what it had been before. Penny felt the door open behind her and moved farther up the ramp to let the guys through.

"Yeah, you didn't answer my question. Who the hell are you people?" The man looked over to the ramp where Sheldon, Howard, Raj, and Leonard were now standing behind Penny, obviously enchanted by the room they found themselves in.

"Right, sorry! Introductions!" The man moved back around to their side of the console. "My name's the Doctor and this is my friend Donna. What's your names?"

"I'm Penny." She elbowed Leonard who was still gaping at the room.

"Huh? Oh, Leonard."

"Sheldon."

"Howard."

Raj just kind of waved.

"Oh, right. This is Raj. Sorry, he can't speak in front of women," Penny explained.

"What, seriously?" Donna asked. Raj sadly shook his head. "Well that's a bit odd."

"Yeah? Try having a box that according to the guys is a space ship from a TV show magically appear in your boyfriend's apartment." Penny's comment made the Doctor look sharply at her.

"Hold on, 'a space ship from a TV show'? What do you mean?"

"You see, you, Donna, and the Tardis exist for us only in a television show called _Doctor Who_," Leonard explained.

"Yes, so either we're all dreaming... ("Oh god, I wish," Penny muttered.) or you slipped through a crack in dimensions and wound up in our world by mistake," Howard added.

"Hold on, we're television characters? Like proper television characters with our own show and everything?" Donna repeated utterly perplexed. "Well that's a new one. I guess it makes a change from being gods, though."

"But how did we get here? There can't be any cracks to slip through. I sealed off the walls between all worlds." The Doctor stated also confused.

"Excuse me, but before this turns into another time where you sulk over losing Rose Tyler, there are more important issues to address," Sheldon walked up the ramp and over to where the Doctor was standing. He held out his hand. The Doctor took it tentatively, and Sheldon firmly shook it. "First, I have to say what a huge honor it is to actually meet you Doctor. You are such a brilliant man. Once you overlook the times you succumbed to romantic entanglements of course." Donna snorted. The Doctor barely had time to register that he should be offended before Sheldon was moving on. "I've often hoped for this opportunity to come. May I have a closer look at the controls of your Tardis? I've always been curious as to the inner workings of Time Lord time and space travel. I have many theories on the subject, but of course, as the human race is far, far behind in terms of technology available, I could never run any tests to be certain."

"I... but... you wa... and s..." The Doctor stammered. Sheldon blinked.

"I'm sorry is that a yes or a no?"

"What?!"

Sheldon turned back to the others. "I may have overestimated his intelligence."

***~~***

_Chapter 2.5 will be up tomorrow!_


	4. Ch 2 part 2: Shouldn't Meet Your Heroes

**The Parallel Worlds Proof**

**A/N: **I may have slipped Sheldon out of character for a brief moment in this installment. It's hard for me to tell. :/ Ah, well it's just for a moment, if I did. Plus this is a crossover. Crack happens. :P Lots of Classic Who references in this chapter for those who are familiar with it. :) And I know I have Howard mention it, but all technical information on the Tardis comes from whoniverse org. Awesome site by the way! Yay semi-accurate technobabble!

**A/N 2:** I won't be able to post the next chapter tomorrow. One, I'll be busy with Christmas and two, I haven't completely gotten past my writer's block yet. :| The plot reached a lull, and I realized I suck at writing downtime.

**Disclaimer:** Don't own anything! Just the DVDs.

**Chapter 2.5 - Shouldn't Meet Your Heroes**

_ "What?!"_

_ Sheldon turned back to the others. "I may have overestimated his intelligence."_

"Oi! I don't know what you are trying to insinuate, but I'll have you know that I am more intelligent than anyone in this room, possibly this entire universe!" The Doctor shouted, indignantly.

"Didn't you almost fail out of the Time Lord Academy?" Howard interjected.

"Oh, you are kidding me!? You didn't?" Donna spun around to face the Doctor who was gaping like a fish. "You did! Oh my god!" She doubled over in a fit of laughter. The Doctor managed to snap his mouth shut and glared down at Donna.

"Stop it! I did not fail out of Academy! I passed my exams thank you very much!"

"The second time." Howard muttered. Leonard and Raj chuckled silently to themselves and exchanged finger-fives with Howard.

"This explains your driving! No wonder we never land where or when we're supposed to." Donna said gasping for breath.

"Actually, that point is debatable," Sheldon said. "Some people claim the Tardis purposely pulls you off course to land in a time and place that requires your assistance. ("Ha!" The Doctor exclaimed triumphantly). Of course, looking at your academic record and comparing your performance to that of other Time Lords we've seen in the show, I'm more inclined to believe you are just a bad driver."

"Ha! Take that Space Man!" Donna shouted at the Doctor. She turned back to Sheldon. "Wait, hold on. 'Other Time Lords'? What other Time Lords? The Doctor says they're all gone."

"So the New Series keeps claiming, but the idea of the Doctor being the only Time Lord left in existence is just absurd. For one thing, the Master has already returned once, and there's no way the Rani wouldn't have entered a battle without some sort of escape plan. She was far too brilliant for that." Sheldon suddenly looked a bit wistful. "Such a remarkable woman. I wish when the show had returned it would have made her the main character. Or at least have brought her back at some point. Her experiments always fascinated me."

Leonard shook his head. "He would relate best to the Rani." Raj and Howard nodded their agreement. The Doctor's eyes were widened in shock and a bit of fear. Donna looked about as lost as Penny was feeling.

"What the hell are you guys talking about?" Penny asked.

"The Rani and the Master are other renegade Time Lords in _Doctor Who_," Leonard said.

"Time Lords?" Penny repeated.

"Yeah. Highly advanced aliens from the planet Gallifrey." Penny continued staring at him blankly. "They used to oversee the events of the universe and uphold the Laws of Time," Leonard continued, "but when the show returned in 2005, the premise included a major Time War between the..."

"Okay, I don't really need the entire story," Penny interrupted. "Why are they here?"

"That's what I'd like to know!" The Doctor exclaimed. "Right behind, where are we and how do you know so much about Time Lords."

"You're in Pasadena, California," Howard said.

"And as to the latter, we already explained. You exist as a television show in this world. I don't see how that is so difficult to comprehend," Sheldon shook his head. "This encounter is becoming more and more disappointing."

"Well they do say you should never meet your heroes," Penny told him. Sheldon looked confused.

"Who says? Is there an organized committee that decides what unlikely social encounters are acceptable and which are not?"

"No, Sheldon. It's just..." Penny tried.

"Do 'they' make special rules for parallel world crossovers?" Sheldon continued on a roll. "What exactly do 'they' say? You can't meet your heroes, but if Dr. Octopus stops by for coffee, have a nice time'?" Everyone stared him with varying degrees of bewilderment and annoyance.

"Anyway," Leonard said turning back to the Doctor, "you have no idea how you guys landed here either?" The Doctor shook his head.

"Not a clue. And now, it seems we're trapped. There's enough power that even if we are in a parallel universe, we should be able to leave, but every time I try and fire up the dematerialization sequence, nothing happens. We're just stuck like something is binding us here. Of course, with our shields down and you lot being able to walk in and out like this really was a phone box, I'd be hesitant to enter the vortex even if we could."

"Did you collide with something in the vortex?" Howard asked. Raj whispered something in Howard's ear causing him to jerk. "Yes, I know it's rare! But so is landing in a parallel universe."

"Well this landing was certainly rougher than normal," Donna answered, watching Raj curiously.

"A collision alone wouldn't be enough to create a breach between universes and knock the Tardis through to our world," Sheldon thought aloud. "Which means the breach existed before the collision."

"Could it be from the reality bomb?' Leonard asked.

"That hasn't happened yet for them," Howard said.

"Yes, but Rose was already crossing universes in 'Partners in Crime'," Leonard countered.

Raj whispered again to Howard. "Series 4, Raj! Watch it some time." Raj frowned. So did the Doctor.

"What do you mean Rose was crossing universes?" the Doctor asked sharply. "When?"

"Strange, I would have thought the phrase 'reality bomb' would have worried you more," Sheldon responded.

"Okay, so the Tardis collided with something in the vortex, damaging the circuitry and shielding. It crash landed here, and now they're stuck. Is that our working hypothesis?" Leonard asked. The other three nodded.

"Right," Sheldon said taking charge. "Doctor, run the fault locater to check the system components. Howard and Leonard, try to locate the dematerialization circuit. I assume it's under the main door control panel judging by the mess of cables stretching out from that section of grating." Sheldon frowned momentarily and muttered, "No semblance of an organization system whatsoever," He shook his head and moved on. "Raj check the force field generator for damage. It's here in the main console room somewhere. I'm going to check the integrity of the sub-neutron circuits. The Vortex shields may have become overloaded by the collision." Sheldon took a step towards Penny. "Ah, Penny..." Penny looked startled.

"What? You want me to do something?"

"No, of course not! You're just blocking my path," Sheldon answered. Penny rolled her eyes and stepped to one side so he could get through.

"One of those, eh?" Donna asked, catching Penny's eye.

"Yep." Penny said. Donna nodded sympathetically.

"Hold on, is the dematerialization circuit the one that looks like a box with things sticking up from it?" Howard asked with gestures miming the shape.

"No that's the force field generator," Sheldon replied. "The dematerialization circuit has got the four branches with thin discs at the end."

"Right, right." Howard crouched next to Leonard and peered down beneath the grating. Raj had already headed off to the right side of the room to pull up the grating there in search of the force field generator.

The Doctor's jaw had dropped nearly to the floor by this point, but he suddenly managed to pull himself together and snapped, "Excuse me! Who do you think is in charge here?! This is MY ship!!"

"Which is why I placed you in charge of running the fault locater. I presume the console screen text is set to Gallifreyan which obviously none of us can read," Sheldon explained. "Now where are the sub-neutron circuits located?"

"You're not touching the sub-neutron circuits! You're not touching anything on this ship!!" He glared at Raj who promptly dropped the grating he was holding with a very loud CLANG. "Who the hell are you people that you know so much about the controls of a Tardis???"

"Just an FYI, I'm a little freaked out by how much you know of a fictional space ship also," Penny piped up.

"It wasn't our fault! Sheldon made us study the technical information of the Tardis controls a few years ago to get our strikes cleared," Leonard explained.

"Yes, The Terrible Backlash of '07. Worst April of my life." Howard said. Raj nodded vigorously in agreement.

"But, where did you get technical information on the Tardis from?" the Doctor questioned, still bewildered.

"whoniverse dot org," Howard answered. "It's a got a compilation of all technical information on Tardis's given out through televised episodes, tie-in novels, audio books, and other officially licensed material."

"There's novels too?" Donna asked, surprised.

"But, no human could possibly understand the inner workings of a Tardis. And they certainly couldn't explain it through a TV show," the Doctor insisted.

"Well, it's not like we really understand how it all works," Leonard admitted.

"Yeah, we never could come to a decision on what exactly 'artron energy' was," Howard added. "Or what the unit 'omega' actually referred to."

"Which is precisely why I wanted to gain access to the Tardis controls," Sheldon said. "Conjecture can only get one so far."

"And you really think you'd be able to understand how the Tardis works just by looking at the circuitry?" the Doctor asked skeptically.

"Of course," Sheldon said in a condescending tone. The Doctor was clearly annoyed.

"Five minutes ago, you were admitting that the human race was incredibly far behind the technology of Time Lords, and yet now you're claiming that you can figure out the technology just by looking at it?! Just who do you think you are?" Sheldon drew himself up to his full height.

"I am Dr. Sheldon Cooper. A highly respected theoretical physicist. I understand everything in the known universe, and I am certain that given adequate access, I can determine the exact nature of every component on this Tardis."

***~~***


	5. Ch 3: Not a Collision

**The Parallel Worlds Proof**

**A/N:** I have no idea if fixed points are so fixed that they exist in every universe, but it sounded good. Plus I needed it for my plot. Also I was sorely tempted to make some sort of reference to Waters of Mars in here, but I managed not too. So still no DW spoilers past Journey's End!

**A/N 2: **I know what I'm doing with Chapter 4 now. It's just a matter of me sitting down in writing it. :P

**Disclaimer:** I do not own the characters or any other recognizable content from The Big Bang Theory or Doctor Who. Unfortunately.

**Chapter 3 - Not a Collision**

_ "I am Dr. Sheldon Cooper. A highly respected theoretical physicist. I understand everything in the known universe, and I am certain that given adequate access, I can determine the exact nature of every component on this Tardis."_

Penny, Leonard, Howard, and Raj were simply shaking their heads or rolling their eyes at Sheldon's arrogant boast. The Doctor, however, shifted from annoyance, to recognition, to disbelief and shock all in a matter of seconds.

"No, no, no, no, no, hold on," he said. "Dr. Sheldon Cooper? THE Dr. Cooper? Which makes.." the Doctor turned to where Howard and Leonard were standing, "you, you're Dr. Leonard Hofstadter." Leonard's jaw dropped "And you're Howard Wolowitz!" the Doctor turned again, "and Raj! Dr. Rajesh Koothrappali! Oh, but this is brilliant!!" The guys were in absolute shock.

"Doctor, who are they?" Donna wanted to know.

"You know them?" Penny asked, confused. The Doctor turned to her.

"I know all of you, Penny. Grew up on a small farm in Nebraska. Left with your boyfriend to find a better life in California, but as typical with young love, things go badly, and you move out across town into an apartment complex. Flat 4B. Across the hall from one Leonard Hofstadter. You change everything. You're amazing!" The Doctor looked around at all of five of them now. "The lot of you! Simply amazing!" He was grinning in gleeful admiration at the scientists. Penny was freaked out.

"Okay, this is some kind of joke or something, right? Who are you? How do you know so much about me?"

"And how do you know our names?"Leonard asked. "We're not even from the same universe."

"Oh, but you exist in our universe too. You exist in every universe," the Doctor explained. "You lot are the most brilliant scientists to come out of the 21st century! I can't believe I'm actually meeting you!" He suddenly rushed around to shake everyone's hand, even Penny's though she refused and backed away. "It is such a huge honor. Really. What year is it for you? Where are you in your research?" Everyone just looked around at each other confused.

"What research?" Howard asked.

"Why, your string theory research of course!" the Doctor exclaimed. "Hold on, hold on. Penny you mentioned 'boyfriend's apartment' earlier so I assume this is around what, 2009? 2010? So you guys have already gone on your famous North Pole trip, correct?"

"Famous?" Leonard repeated. Raj scoffed.

"Perhaps you mean infamous," Sheldon suggested. "That was not a trip that went well."

"What are you talking about? You proved the existence of monopoles! A crucial step to proving string theory!" The Doctor reminded them.

"On the contrary, the positive data readings were just _somebody_ turning on and off the electric can opener," Sheldon glared over at Leonard.

"We said we were sorry, Sheldon!" Leonard cried. "Multiple times in fact!"

"Yes, well 'sorry' doesn't erase the embarrassment of having to send out a retraction email to everyone at the university nor it does it erase all the snide comments Kripke has made since then."

"Electric can opener? Retraction email? But, that's not right. Summer 2009. You went to the North Pole. You recorded data that definitively proved the existence of monopoles. It changed the way people viewed the universe!"

"Maybe in your world. But here we just definitively proved that being locked up with Sheldon for three months is pure hell," Howard said dejectedly.

"No, but your discovery is a fixed point. Like Pompeii. It happens in every universe. You were supposed to get positive data at the North Pole," the Doctor insisted.

"Fixed point? What does that mean? Like destiny?" Penny asked.

"In a way," the Doctor allowed.

"So something messed up their time line. Is that why we can't leave?" Donna asked. The Doctor spun around to face her. An epiphany struck him.

"The collision. Of course!!" He raced around to the console screen again. "It wasn't a collision at all! It was a wound in time, bleeding through across the universes. It disrupted the flow of chrono energy, created a storm. It was practically a tidal wave that we hit! We got sucked through the vortex to the source of the wound, and now we're trapped here."

"But why are the defenses down?" Donna asked.

"Not sure," the Doctor frowned. "Must have been caused by the wound. This is a massive disruption in time, having a fixed point altered like that. There's no telling what the repercussions of that may be. We need to pinpoint the moment it got off track! Tell me," he looked at Leonard, "what happened on July 20th? Exactly, now. Every tiny detail."

Leonard was baffled. "July 20th? I don't know. We were at the North Pole obviously, oh wait. That was..." he trailed off uncomfortably. The other three obviously recalled the events too as the guys began to shift awkwardly and seemed determined not to make eye contact with anyone.

"What?" Penny asked.

"We agreed never to discuss that day," Howard stated, staring at the floor. "Ever," he added more sternly, briefly glaring at Sheldon.

"It's not that big of deal," Sheldon insisted. "We just..."

"Nuhehehe!!" Howard cut him off. "Never."

"Look there is a massive wound in time that's affecting more than one universe. Reapers could start showing up at any moment. I NEED to know, what happened on July 20th?"

Leonard bit his lip. "That was the day the heater went out," he admitted.

"Yes, and that's all we're going to say on the subject," Howard added.

"The heater went out?" the Doctor was confused. "What like electrical problems?"

"As far as we can tell," Leonard said. "Something overloaded the fuse box, and when we got the power back, the heater wouldn't turn on."

"So you weren't able to collect any data?"

Sheldon shook his head. "Not that day."

"But, but, why did the fuse box overload??" The guys just shrugged. The Doctor turned back to his screen and began flipping switches and pushing buttons.

"What are you doing?' Howard asked.

"I'm using the Tardis to trace the time lines back to determine the moment they veered off course. There must be something more going on here than broken heaters," the Doctor said.

"Hold on, are you saying our equipment was purposely sabotaged?" Leonard asked.

"Maybe, but why would they do it? How could things get so twisted around?" the Doctor wondered, running his hands through his hair.

"How long will it take to trace the time lines?" Donna asked.

"A while. There's a lot of variables to work through," the Doctor replied.

"I'd better call Bernadette and tell her I'm going to be late." Howard reached for his phone and then hesitated. "Do I mention the Doctor and the Tardis?"

"No!" Penny looked at him like he was insane.

"Point. She'd only think I was joking anyway." Howard walked back into the apartment to make the call.

"I'm going to go change. I need to get out of this crazy box," Penny exited also. Leonard watched her leave.

"Anyone up for a cuppa?" Donna asked.

***~~***


	6. Ch 4: Ready? Fight!

**The Parallel Worlds Proof**

**A/N:** Finally worked through the block I was getting with Chapter 4! Apparently my solution to a lull is to have everyone argue! lol I already know where this is heading so there shouldn't be any delays with Chapter 5. The following events may seem to interfere with "Turn Left", but since Donna didn't realize the Time Beetle was with the Fortune Teller, I figured I could get away with this.

**Disclaimer:** I don't own Doctor Who or The Big Bang Theory. If I did, I wouldn't be so annoyed with the wait for new episodes. :P

**Chapter 4: Ready? Fight!  
**

Penny burst into her apartment and immediately forgot what she had meant to do. In her defense, she had a lot on her mind. A large blue box that somehow housed a spaceship from a TV show had just shown up in her boyfriend's apartment along with an insane alien who somehow knew the story of her entire life. To say Penny was freaked would be an understatement. Looking around, she spotted the bottle of wine on top of her refrigerator. Perfect. She'd have a couple of glasses, get out of her work clothes, and take a shower . Then maybe when she went back over to Leonard's, she'd find out the entire thing had been one big dream. _'Please, please just be a dream,'_ she thought as she downed the first glass of wine.

**~**

Sheldon had insisted on following Donna to the kitchen to oversee the tea production so Leonard and Raj were left alone with the Doctor in the console room. The Doctor seemed pretty preoccupied with tracing the time lines. Raj stood awkwardly for a second and looked over at Leonard. "Now what?"

Leonard shrugged. "Beats me,"

Raj shifted in place a couple of times before looking back up at Leonard. He grinned really big. "We're a fixed point in time," he said proudly.

Leonard couldn't help the grin came across his face. "Yeah, that is pretty cool!" Raj nodded, still grinning.

A couple minutes passed where the only sounds were the Doctor's frustrated sighs and the clicking of buttons and switches. Raj and Leonard were each lost in their own thoughts. Finally, Leonard frowned. "How did our equipment get damaged, though?" Raj thought for a second.

"Maybe it was the Daleks," he suggested.

Leonard looked at him, skeptically. "The Daleks?"

Raj shrugged. "Sure. The Emperor needed to stall scientific research in order to gain control over the human race so he sent in some Daleks to overload our fuse box, thus preventing us from obtaining the correct data."

Leonard blinked a couple of times. Then he exclaimed, "That's ridiculous!"

"No it's not! The Emperor used the media to control the human race in series one! Why is it so ridiculous that he is controlling the advancement of science?"

"Well for one thing, the Emperor has been disintegrated into dust." Raj huffed in annoyance. "And for another thing," Leonard continued, "the Daleks are not involved in every catastrophe in the universe!"

"Oh come on. They're the Daleks, dude! They're like the original sci-fi badasses."

"Oh, yeah. They're so badass when you run up the stairs and can escape because the Daleks get stuck at the base of the stairwell."

"Hey! They can elevate now!" Raj defended.

"So what? They're insane!"

"Which is why they tampered with our equipment!"

"The Daleks did not tamper with our equipment! There are other villains in _Doctor Who_! Right Sheldon?" Leonard called out as he saw Sheldon and Donna return to the control room with their tea.

"Of course, there are other villains in _Doctor Who_. There are the Cybermen, the Slytheen, the Autons, the Sea Devils, the Sontorans, the Master, the Vashta Nerada..."

"The Trickster's Brigade!" the Doctor exclaimed suddenly.

"Yes. The Trickster and his accomplices," Sheldon agreed. "Though he seems to be used more often in _The Sarah Jane Adventures_ than in _Doctor Who_."

"No, a member of the Trickster's Brigade is what caused the your time line to become skewed," the Doctor clarified.

"The Tardis finished the trace?" Leonard asked, going over to peer at the screen. Sheldon and Raj followed.

"Yep," the Doctor said. "12th of January 2009. The Tardis found elements of the Time Beetle's biostamp. Can't tell what it changed, but whatever it was set off a chain of events that led to your power going out that day in July."

"What? One little beetle in January caused all of this to happen?" Donna asked.

"The Time Beetle isn't just any beetle. It changes key decisions in people's lives and then feeds off the energy of the lost time line. But this moment is strange. It doesn't seem to have changed any decision. The time lines just get muddled that day and wind up branching off just slightly in the wrong direction." The Doctor frowned at the screen.

"Just slightly in the wrong direction? We were supposed to get positive readings and didn't, and now there's a gaping wound in time that's bleeding through to your universe. Sounds like things went in a _very_ wrong direction." Leonard said.

"Weeeeellll, sure by now, the time line is heading in completely the wrong direction, but in January it was just a little problem," the Doctor explained. "Something small. Something simple that the Time Beetle changed. What was it though?" He adjusted some knobs, trying to bring the events of January 12th into better focus.

"Let's see. January 12th. That was the day we completed Monte," Sheldon stated. He sighed. "Oh, Monte. How I miss you."

"Who's Monte?" Donna asked.

"Our killer robot," Leonard explained. "He got destroyed in an unsanctioned fight because _somebody_ let their pride get in the way." He and Raj both glared over at Sheldon with that statement.

"Well, it wasn't like we could have backed down!" Sheldon responded. "Kripke challenged us so we had to fight."

"You knew we were doomed without Wolowitz! You should have called it off, Sheldon!" Leonard yelled.

"Oi!!" the Doctor shouted, cutting off Sheldon who had been about to continue the argument. "We're trying to track down where your time lines went wrong! Not argue over who's to blame for your robot being destroyed." The guys fell silent, though, they still shot glares at each other. "That's better. Now! You finished your robot. What else happened that day?"

"Nothing," Leonard said. "We tested the robot out on a couple of things, got dinner, watched some TV and went to bed." Raj leaned over and whispered into Leonard's ear. "Oh, right! Penny chewed out Howard for being creepy, and he wound up hiding out in his room for a couple of days. That's why he wasn't there to help improve Monte before the showdown with Kripke."

The Doctor frowned. "You keep mentioning this Kripke fellow. Who is he?"

"My sworn enemy. He destroyed my robot. He pumped helium into my office during my NPR interview. He constantly mocks me. And to top it off, he hates monkeys," Sheldon said bitterly.

"Sounds like a right twat to me," Donna said. "Do you think he's involved, Doctor?"

"Not sure. It seems like he may be. His name keeps popping up with every event that went wrong so far. But why? What are we missing? Think, think, think, think." The Doctor started pacing. "Something small. Something small. You finished a fighting robot. Penny yelled at Howard."

"Hey-o! Someone say my name?" Howard said, returning to the Tardis.

"Hey, what did you tell Bernadette?" Leonard asked.

"I just told her an emergency came up at work, and I may not be able to take her out tonight. She seemed okay with it."

"She probably wasn't very shocked by that story. You have quite a few emergencies occur with your work," Sheldon said.

"I do not have quite a few emergencies occur!" Howard exclaimed.

"You once had us up all night trying to fix your space toilet!" Leonard retorted.

"Okay, yes. There was that incident with the space toilet. But that was it!"

Raj whispered in Howard's ear. Howard shifted irritated. "Fine, I guess I did kind of get the Mars Rover stuck in a ditch."

"Kind of?!" Leonard questioned.

"Alright!" Donna interrupted. "Doctor have you figured out what any of _this_," she waved her hands around in the air, "means yet?"

"Nope. Haven't the foggiest," the Doctor admitted.

"Well how about you hurry up and sort it before this lot starts killing each other."

"We weren't going to kill each other," Howard said grumpily.

"Hold on, who's Bernadette?" the Doctor suddenly wanted to know.

"My girlfriend," Howard said proudly.

"Girlfriend?" the Doctor asked confused. "What girlfriend?"

"My girlfriend, Bernadette. She works at The Cheesecake Factory and is going to grad school for microbiology," Howard explained. The Doctor was still lost.

"But you don't have girlfriends. Weeell, okay after the Nobel Prize, you have some brief relationships with women who might be classified as your 'girlfriend'. But you certainly don't have any girlfriends now. It's impossible! The whole idea is just absurd!"

Stunned silence followed that statement. Raj leaned over and whispered, _"Harsh,"_ in Leonard's ear. Leonard nodded in agreement.

Donna crept over to the Doctor and whispered, "A bit rude there."

The Doctor turned to look at her. "Was it?" Donna nodded. The Doctor frowned. "I really need to work on that."

"Hang on! Howard wins a Nobel Prize?!" Sheldon exclaimed in shock.

***~~***

**A/N 2:** Seemed as good as place as any to end a chapter. :) I thought we'd check back in on Penny by the end of this chapter, but too many little arguments and discoveries were going on. We will check back with her soon to make sure she didn't get too freaked out by the Tardis (or go overboard with the wine :P ).


	7. Ch 5: Broken Nose Equals Girlfriend?

**The Parallel Worlds Proof**

**A/N:** You know I have almost the whole exchange between Leonard and Penny written out, and I STILL haven't reached the point of the story where I can add that in. *shakes head* Too much plot to wade through. On the upside, I finally utilized Donna! A little bit anyway. I felt bad because I haven't been doing much with her. :|

**Disclaimer: **Still own nothing. :P

**Chapter 5: Broken Nose = Girlfriend(?!)**

_"Hang on! Howard wins a Nobel Prize?!" Sheldon exclaimed in shock._

"Why can't I have a girlfriend???!" Howard demanded.

"How could YOU win a Nobel Prize?!" Sheldon cried.

"Bernadette. Kripke. All these names! I don't recognize them, but somehow they're important," the Doctor was running his hands through his hair again, obviously frustrated.

"No, seriously. I want to know. Why is it impossible for me to have a girlfriend?" Howard asked again, this time with a hint of panic in his voice.

"I don't understand it. You don't even have a PhD! And you're a mediocre engineer at best. How could anyone possibly award you a Nobel Prize?" Sheldon pondered.

"January 12th. Nothing happened that day. It was just a fighting robot.," the Doctor continued, thinking aloud, and completely ignoring everyone else. "Nothing out of the ordinary. Building a robot. Losing a fight. Building a robot. Think, think, think! What was it? What's different?" He paused. He looked over at Howard. "You lost the fight. You lost the fight, because you weren't there. Why weren't you there?"

"I was otherwise detained," Howard said, looking down at his feet. Raj whispered in Leonard's ear.

"Yes! I got it, Raj," Leonard told him. He addressed the Doctor, "Penny had yelled at him the day we finished Monte. It hurt Howard's feelings so Howard locked himself in his room and refused to come out." Raj whispered furiously in Leonard's ear again. Leonard shook his head. "No, that's not the wording you used. I thought we'd try being a little nice for once." Raj rolled his eyes.

"Why did Penny hurt your feelings?" Donna asked.

"Uh, I don't know. She must have just been in one of those moods," Howard said, shrugging. Raj went over and whispered the real reason to Howard. Howard glared at Raj. "Yes, thank you, Raj!" Raj smiled and then nodded his head in Donna's direction. Howard shifted and reluctantly admitted, "I was being overly 'creepy' apparently that day so Penny chewed me out."

"Creepy? What were you doing?" Donna asked, confused.

"He was hitting on her, like he always does, but that time he refused to stop or shut up," Leonard said, shooting Howard a stern look. Howard glared back.

None of this was helping the Doctor, though. "Something still isn't adding up," he insisted. "Something is off in this story, but I can't figure out what." He started flicking switches and twisting knobs again, bringing up something else on the screen.

"What are you doing?" Leonard asked.

"I'm pulling up your biographies from the Tardis library. Maybe this robot fight was mentioned. It could help us pinpoint what's different in your time line," the Doctor replied, concentrating on the screen.

"But that's cheating! You're a Time Lord. You should be able to remember these things," Sheldon criticized.

The Doctor tilted his head up to glare at him. "You really expect me to remember every single detail of every single person's life?"

"If they're important people like me, then yes," Sheldon replied. The Doctor shook his head and returned to scanning the screen.

He flipped through what looked like hundreds of pages at a lightning pace before finally exclaiming, "Ah ha! Here we go! Monte, the killer robot. Completed January 12, 2009. You fought your rival, Barry Kripke in an unsanctioned fight on January 14th. You were victorious and Kripke never bothered you again. It seemed to be a major boost for your self-esteem, too."

"Hang on, we were victorious? How?" Leonard and the guys crowded around the console screen to read, shoving the Doctor away in the process.

"'They got the edge by viewing YouTube footage of Kripke's previous battles and practice runs,'" Sheldon read.

"'Wolowitz added side blades and extended the front arm to allow for a larger range'?" Leonard also read.

"So I was there to make improvements?"

"Apparently."

"So wait, does that mean Penny never chewed me out? Or did she apologize earlier?"

"There's nothing here about an argument between you and Penny," Sheldon said reading the page completely. "Nor is there any mention of you getting punched in the nose." Howard glared at him.

"So what. The argument never took place?" Leonard asked.

"It would seem so," Sheldon answered.

"Maybe that's why you don't have a girlfriend." Everyone looked over at Donna.

"How is that relevant?" Sheldon asked.

"I'd like to know that, too," the Doctor said, looking just as lost as the other four.

"Seriously? You don't see the relevance?" The guys exchanged blank looks and shook their heads. Donna gave an exasperated sigh. "It sounds like Howard, there, needed a lesson in how to talk to women properly. Penny calling him out on his inappropriate behavior and punching him in the nose was just the wake-up call he needed."

"But Howard still hit on Penny and any other woman he came into contact with," Leonard contradicted.

"Oh, yeah," said Howard, nodding in agreement.

"But you said you have a girlfriend now," Donna pointed out.

"Yeah," Howard said, slowly.

"Did you have a girlfriend in the other time line?"

"No," the Doctor answered.

"Then, there you go," Donna finished.

"So hold on," Howard said, still trying to work this out. "You're saying, I only have a girlfriend now because Penny punched me in the face last January?"

"Huh," said Leonard.

"So it's Penny's fault Monte is dead," Sheldon reasoned. He hit Leonard on the arm. "I told you not to say 'hello' to her!" Leonard just ignored him.

"Brilliant Donna!" the Doctor exclaimed. "Now we know the altered event!" He pulled up the time line trace again.

"So the Time Beetle caused Penny to yell at Howard?" Leonard asked.

"More likely it changed something that led to that argument," the Doctor clarified, "but the time lines are so fuzzy that day, we can't narrow it down to a more precise change."

"But how does Penny punching Howard in the nose affect our heater going out at the North Pole?" Sheldon questioned, utterly perplexed.

"Don't you see? There were other repercussions from that event. You lost the fight to Kripke! You were supposed to win. You would have gained a grudging respect from Kripke, and he would have left you alone after that."

"But instead we lost, and he continued to mock us and give us a hard time," Leonard said, picking up on the train of thought.

"Oh, my..did Kripke sabotage our equipment?!!!" Sheldon shouted.

"Here it is! Tenth of May 2009. Barry Kripke, quite clearly, crept into your lab and damaged some of the wiring. Eventually, it would lead to your fuse box overloading. And the day that occurred on just so happened to be the day you would first record some positive data. Real positive data. Not electric can openers." The Doctor looked triumphantly around. "We solved it!"

"Great. Now how do we fix it?" Howard asked.

The Doctor opened his mouth, closed it again, the opened it again. "Ah."

***~~***


	8. Ch 6: Half Past Weird

**The Parallel Worlds Proof**

**A/N:** Finally got this done! Sorry it took me so long! I went out of state for the New Years so I wasn't able to work on it for a few days. Future updates will probably occur every few days. I have classes starting back up soon so I won't be able to update every day like I did in the beginning. I do promise that this fic will NOT be abandoned! There's nothing worse than getting 8 chapters into a story only for the author to disappear and never finish the fic.

This chapter is a bit longer I think. We finally check back in with Penny! Also I have no idea what Hollywood actor Donna would most want to meet so I just went with the first name that popped into my head. If you have any better suggestions, feel free to let me know! I can easily change the name. :)

**Chapter 6: Half Past Weird and Quarter to Terrifying  
**

There was quite a bit of arguing that followed as the Doctor and the guys sought a solution to their messed up time lines. Obviously, they needed to go back in time and undo the Time Beetle's work. Unfortunately, the Tardis was still stuck in Leonard and Sheldon's apartment.

"What about the artron filaments?" asked Sheldon.

"No fault," the Doctor responded.

"The multi-loop stabilizer?"

"No fault. There isn't anything wrong with the circuitry!"

"Did you rerun the fault locater?"

"I've ran it three times, Sheldon! There're no faults!" the Doctor cried. "It must be the wound in time holding us here. We can't move the Tardis."

"Well how are we going to fix the time lines so I can accept my Nobel Prize?"

"I don't know! How about you shut it and let me figure it out!"

"Let _you_ figure it out? What makes you qualified to find the solution?"

"I'm the Time Lord!!!"

"Well, you have to admit, you're not a very good one. You couldn't even remember the correct details on our robot fight without checking our biographies!"

The Doctor was looking murderous. Donna turned to the other three, stunned. "Is he always like this?" Leonard, Howard, and Raj all nodded.

Leonard decided to try to interfere. "Hey Sheldon, probably not a good idea to insult the 1000 year old Time Lord who's trying to help us."

"Yeah, he does have the nickname 'The Oncoming Storm' for a reason," Howard added.

"No he doesn't," Sheldon disagreed. "That's an invention of Russell T. Davies. The Daleks never once called him that in the Classic Series."

"That's it!" the Doctor shouted. Everyone looked at him startled. "All of you out! Leave the Tardis now!! I'm not having you in here bothering me while I'm trying to work out how to fix YOUR mess!"

"We didn't cause the mess. The Time Beetle did," Sheldon argued. Leonard grabbed his arm and started tugging him towards the door.

"He knows, Sheldon. Let's go before he chains you up in the dungeon and leaves you there to rot."

"The Tardis doesn't have a dungeon."

"It'll build one special for you," Howard said, also working on shoving Sheldon out the door. "Now move!"

The guys piled out of the Tardis, followed a few seconds later by Donna. They turned to look at her.

"Oh, he was kicking you out too?" Leonard asked. Donna shrugged.

"It's safer this way."

"Ah," Leonard said, nodding.

There was a few moments of silence while the guys shifted awkwardly and looked around a bit lost. Donna tried to rescue them.

"Sooooo, Pasadena, California, eh? Where's that then?" The guys stared at her blankly.

"Do you really not know where it is or are you just trying to make awkward small talk?" Sheldon asked. Donna shrugged, feeling a bit uncomfortable.

"I'm from Chiswick. I don't know every city in California."

"Pasadena is just outside of Los Angeles," Leonard supplied, helpfully.

"You mean Hollywood?" Donna asked eagerly, her eyes lighting up. "Blimey, I've never been to Hollywood before! I'll have to drag the Doctor out for some sightseeing before we leave."

"Sure but you're in the wrong universe. It'd probably be safer if you went back to your own universe for sightseeing when this is over," Howard said. Donna waved him off.

"Fine, whatever. As long as the Doctor helps me meet Brad Pitt, I'm happy."

"Who?" Leonard asked while Sheldon gave a frustrated sigh.

"Of all the companions we could have been stuck with, it had to be Donna Noble." Sheldon shook his head sadly.

"And what's that supposed to mean?" Donna said, highly offended.

"Yeah, Sheldon, come on. Donna is awesome! Best New Series companion hands down," Howard stated.

"Yeah!" Donna exclaimed. "Wait, seriously?" She turned to ask Howard.

"Well that's not much of a competition. So far everyone else in the New Series has been far too concerned with love and sex rather than learning about the universe. At least Donna knew better than to harbor romantic feelings toward the Doctor."

"Of course I'm not going to harbor romantic feelings for skinny Alien Boy! He's like stick skinny! And an alien!!" Donna shouted.

"Hey, Rose certainly held her own! She'd just get a bit sidetracked if she was around the Tenth Doctor," Howard argued. Sheldon rolled his eyes.

"You know, I'm going to go check on Penny," Leonard raised his voice a bit in an attempt to be heard. It didn't matter. No one noticed as he slipped out the door and went across the hall.

"You only like Rose, because you thought she was attractive," Sheldon claimed.

Raj and Howard exchanged looks and turned back to Sheldon. "Um, duh! Rose was hot!" Raj nodded his agreement. "All the companions have been." Howard suddenly spun around to Donna. "Seriously, if I didn't have a girlfriend right now, I'd..."

"I will smack you," Donna interrupted.

"Alright," Howard turned away.

**~**

Leonard knocked on Penny's door before poking his head into the apartment. "Penny?" He called. He heard the shower shut off. He walked into the apartment and shut the door behind him. Penny came out wrapped in a towel a minute later.

"Hey," she said.

"Hey," Leonard answered. "Trying not to smell like cheesecake?"

"Trying to drown myself more like," Penny said, sounding a bit on edge. She began searching through the clothes scattered about the living room. Leonard just nodded.

"Did the wine help?" He asked, spying the opened bottle on the counter.

"Is that box still in your apartment?" Penny asked.

"Yep."

"Then, no," Penny answered, finally coming up with the sweatshirt she had been looking for. She walked back into her bedroom to get dressed. Leonard hesitated, trying to think of something to say.

"You know, Penny, it's not that weird that the Doctor is here. I mean yes, he is technically a television character in our world, but _Doctor Who_ is sci-fi, and really anything is possible in sci-fi and ...." Leonard trailed off as Penny walked slowly out of the bedroom, now fully dressed, arms folded across her chest, hair dripping water on her sweatshirt, and eyes shooting him a death glare. Leonard gulped.

"It's not that weird?" Penny began quietly. '_Here we go,'_ Leonard thought apprehensively. "There's a spaceship that's bigger on the inside sitting in your living room. There's television characters walking around who somehow recognize our names. We're way past weird, Leonard! That's terrifying!" Penny practically shouted. Leonard realized Penny was probably right at least when looking at the situation from a non-science-fiction fan's point-of-view, but he had no idea what the correct thing to say would be at the moment so he just sort of frowned and bit his lip. Penny dropped her gaze and let out a frustrated sigh. She looked back up at Leonard a moment later, annoyance giving way to fear. "How did he know all those things about me?" Leonard frowned deeper. He hadn't really taken note of what the Doctor was rattling off earlier. He was too shocked that the Doctor had recognized and knew their names as if they were someone important. Which apparently they were. Or at least were supposed to be.

"You're important," Leonard said, still lost in thought.

"What?" Penny was confused.

"That's why the Doctor knew us. We're all important," Leonard continued.

"Yes, you guys prove string theory and become famous scientists, but I'm nobody! I'm not important," Penny insisted. Leonard snapped out of his thoughts and looked at Penny.

"He said 'you change everything'," he recalled.

"But what does that mean?"

Leonard shrugged. "I don't know. Donna figured out that Howard only has a girlfriend because you punched him last January. Maybe it's because of you we are able to prove string theory."

"Okay, now that's just ridiculous. I don't know anything about physics!" Leonard looked at her pointedly. "Well I don't know anything that would help prove string theory," Penny corrected. "The little I do know was what you taught me. And how does Donna know I punched Howard?"

"Oh! We worked out where the time lines went wrong after you left. It dates all the way back to when we built our killer robot. In the correct time line, you didn't yell at Howard, Howard didn't wind up sulking in his room, we actually defeated Kripke in the robot battle, and Kripke didn't sabotage our equipment so we were able to record positive data."

"Great so this is all actually my fault! Perfect!" Penny huffed and went to get more wine.

"No it's not!" Leonard rushed over to cut her off. "It was a Time Beetle that altered the time lines. It feeds on excess chrono energy given off by going back in time and changing key decisions in someone's life. Whatever it changed in our world, led to you yelling at Howard. But you are not personally responsible for the time lines getting off course."

Penny stared blankly at him. "I have no idea what that means."

"It means it's not your fault," Leonard told her. Penny narrowed her eyes suspiciously.

"Promise?"

"Promise." Penny continued to eye him suspiciously for another moment or two before she finally relaxed.

"Okay, good. Because I did not want _that_ to be the reason why the Doctor knows me."

"No, I think he knows you for something in the correct time line. After all, Bernadette isn't in the correct time line, so the Doctor didn't know anything about her."

"Hang on," Penny said, her eyes widening, "you said Howard wasn't supposed to have a girlfriend in the 'correct time line' or whatever, right?"

"Right. Because you didn't teach him a lesson on how to treat women by punching him in the face." Leonard smiled at her, but Penny didn't smile back.

"Okay so Howard doesn't have a girlfriend. Do you think that you and I....?" Leonard's smile faded quickly.

"No. No we..because you even said that we were... and.. and the Doctor didn't...he didn't say anything to..." Leonard paused, frowning. "You know we should probably check on that."

"Uh, huh," Penny agreed, closely following Leonard as he turned to rush back over to the Tardis.

***~~***


	9. Ch 7: Project the Solution & Say Goodbye

**The Parallel Worlds Proof**

**A/N:** I can't even begin to apologize for how long it took me to finish this last chapter, but I'll try anyway. I am so, so sorry for the long wait!! I have no excuses. I just fail.

I was planning on splitting the end into two chapters, but when I finally got around to writing it, I just wanted to get it done. Hence, the insanely long chapter. I actually have a short epilogue I want to write, but it has nothing to do with the plot. It's more of a tongue-in-cheek type of scene. *winks* It requires me to look up some info on an old sci-fi book which I don't have time to do at the moment so the epilogue won't be up until tomorrow. But the actual story part of this fic is finally finished! *celebrates* Hope you enjoy!

**Chapter 7: Project the Solution and Say Goodbye**

"Oh, really, great Dr. Cooper? Stitch this!"

_Smack!_

Sheldon recoiled and grasped his cheek. His lower lip quivered a little as Donna continued berating him.

"Call me an idiot again and I'm going to knock you halfway to Mars! Got that?" Sheldon meekly nodded.

"What's going on?" Leonard walked in and asked.

"Sheldon insulted Donna. Donna gave him one of her patent slaps." Howard said.

"Where's Raj?" Penny asked.

"He ran off to the bathroom as soon as Donna started shouting."

"Sheldon didn't you realize making Donna angry was a bad idea? They weren't exaggerating about her slaps."

"Yes, well I am aware of that now, thank you. Very aware." Sheldon groaned and rubbed his cheek. The Doctor suddenly poked his head out of the Tardis.

"If you lot are done chatting, I believe I found our solution." He disappeared back inside. The group looked at each other for a second then piled inside.

"Raj! The Doctor's figured it out!" Howard turned back and called from the doorway.

Inside, the Doctor was at the console screen, making some adjustments to the knobs nearby.

"So, what's the plan?" Donna asked, coming over to stand next to him. The rest of the group filled in around the central console. Raj walked in just behind them and made sure to stand on the very opposite side from Donna.

"Were you able to get the Tardis to move? Leonard asked.

"Nope."

"Then why did you say you have a solution?"

"Because I do! We may not be able to move the Tardis, but we can still move ourselves." Howard's eyes lit up.

"Projection?" he asked.

"Precisely!" The Doctor said. "Now since there is no possible way to reason with a Time Beetle, I have to find a place in the time line that I can change."

"So you'll send a projection and prevent Penny from criticizing Howard?" asked Sheldon.

"Yeah like that will work," Penny muttered.

"My thoughts," agreed the Doctor. "So instead, I'm..."

"Going to convince Howard to help out with the robot anyway?" asks Leonard.

"No, I'm going to..."

"Instruct them on how to improve the robot without Howard?" asks Donna.

"No! Now will you let me finish?!" exclaimed the Doctor, obviously getting frustrated. Everyone stayed silent, finally. "Thank you. Now since the days leading up to the robot battle are so muddled up, I thought it best to send a projection back to May 14th and prevent Kripke from damaging your equipment. You still get your positive readings, Kripke can no longer criticize you, and Howard gets to keep his girlfriend. Everybody wins!" the Doctor grinned at his brilliant plan.

"The Nobel Prize. Everybody wins the Nobel Prize," Sheldon clarified.

"Yes, yes, that too."

"So who's being projected back?" Leonard asked.

"Well me of course!" the Doctor said as if that should be obvious. Penny and Donna rolled their eyes.

***~~***

Barry Kripke walked carefully down the hallway. He smiled and said 'Good morning' to Dr. Gablehauser as he passed. Barry watched him until he rounded the corner and disappeared. He was alone in the hall now. Quietly he moved over to the door on the left and pulled out a ring of keys from his pocket. Head down, he concentrated on locating the correct key.

"Tsk tsk tsk. Barry Kripke."

Barry's head whipped up in shock and he quickly shoved the keys behind his back. He spun around expecting to see Dr. Gablehauser standing in front of him, but instead found himself facing a tall, lanky man with spiky brown hair dressed in a pinstripe suit. Barry's jaw dropped.

"Ah, I see you also recognize me!" the Doctor noted. "Must be a fan of my show. That's nice. Now! I bet you're wondering how I got here. Well, you see I fell through a crack in dimensions that your little prank there ends up causing. You meddling with a fixed point in time, Barry. And we both know what that means. Trouble. With a capital 'T'. Whole universes will start collapsing if you continue with your plan so unless you want to watch this world crash and burn until reapers come to purge the wound, I suggest you turn around, wander back over to your own lab and leave Dr. Cooper and his pals alone, capiche?"

Barry stood frozen in place. The Doctor sighed.

"Right, let's try it this way. Run!"

Barry's eyes widened at the command and finally began to back up a few steps. He stumbled a bit as he turned around and then he was sprinting down the hall, snatching glances over his shoulder.

The Doctor smirked.

***~~***

"Brilliant! All fixed now." The Doctor clapped his hands together. "The time lines should sort themselves out after we leave."

"And I'll get my Nobel Prize?" Sheldon double-checked.

"Yep! All of you will." The guys whooped with excitement and exchanged some high-fives.

"Doctor, you rock!" Howard shouted.

"No kidding!" Leonard agreed while Raj nodded fervently.

"So now we can be off?" Donna asked. The Doctor went back to the screen and typed in some commands.

"Yes! The time lines are already starting to shift. The Tardis can free herself and take us back to our own universe again. But there's still one more thing that needs to be done before we can go."

"What's that?" Sheldon asked.

The Doctor pointed at the wires and cables still strewn across the floor. "You four are cleaning this mess up."

***~~***

Donna placed herself in charge of overseeing the cleaning process, much to the guys' dismay. Penny stood at the outer edge of the room, trying to stay out of everyone's way. The Doctor saw this and decided now would be a good time to talk to her. Reading a third party account of a situation was fine when you wanted the facts, but when you wanted to know what something was really like, you need to talk to the people directly involved. That's part of why he traveled. And right now, he was itching to learn more about Penny's involvement in the scientists' lives. She left too quickly earlier for him to get a good read on her interactions with the guys. He was curious how she managed to play such an important role in proving string theory.

"Feeling better now?"

Penny looked up, startled to see the Doctor standing beside her. "Um, what?"

The Doctor shrugged. "You seemed a bit less comfortable than your friends with an alien spaceship landing in your living room."

Penny laughed. "Yeah, you could say that." She paused then added. "I don't really get into the whole sci-fi thing. I mean I watch it with the guys, like Battlestar and stuff. But I don't get excited about it, and I am definitely not okay with television characters suddenly showing up."

"Yeah, sorry about that. Honestly, didn't mean to, but trouble just seems to pull me in whether I was looking for it or not." He grinned. "It does make things more fun." Penny looked at him like he was insane.

"You're like Leonard and them aren't you? I mean, yeah, you're apparently an alien and everything, but your also just like them. A nerdy genius."

"Well, I don't like to brag, but yeah." Penny rolled her eyes and laughed.

"And the ego to go with it." She smirked. "Though, still not as big as Sheldon's."

"Ah, yes, Dr. Cooper. I've read his autobiography."

"What was it? Five hundred pages of how brilliant he is?"

"Pretty much."

Penny rolled her eyes again. Then she eyed him suspiciously. "So, assuming this isn't all just one big dream, you are an alien that travels through time and space getting into trouble?"

"Weeeell, and also having fun! But basically, yes."

"So what planet are you from again? Mars?" This made the Doctor laugh.

"Goodness, you sound like Donna, now. No, I'm not from Mars."

"Then where are you from?"

The Doctor took a deep breath. "From a planet that doesn't exist anymore." Something in his tone told Penny she shouldn't push the subject any further.

"I'm sorry."

The Doctor shrugged it off and turned back to look at her. "So, let me ask you something Penny, how did you meet this lot?"

"I thought you said you knew everything about us?"

"I do! I just want to hear it from you."

Penny shrugged. "There's not much to it. I moved in across the hall from Leonard and Sheldon after I broke up with my boyfriend. Leonard saw me, and they came over to say hi."

"And Leonard invited you over for lunch."

"Yeah. And I wound up using his shower. He and Sheldon wound up losing their pants when they tried to get my TV, and I took all four of them out for dinner."

"Why did you keep hanging out with them?"

Penny looked at him weird again. "What? What do you mean, 'why'?"

"I mean, why did you keep talking to them? What made you five become friends?"

Penny was taken aback by the question. "I don't know. Just did." She frowned in thought. "They were just so different from anyone I'd ever met before. They seemed genuine. No, they _were_ genuine. They were exactly who they said they were. No pretense or alternate personality to hide behind. They were just, them." Penny shrugged. "I liked that. It meant I could actually be me around them. I could actually trust them. I don't know, I just felt comfortable around them. Even though I didn't understand most of what they said." She chuckled. "Still don't, really." She gazed over to where Leonard and Raj were bickering with themselves over exactly where a particular cable went. The Doctor watched her carefully for a few moments.

"That worries you, doesn't it?"

Penny blinked in surprise and looked back at him, eyes wide. "What?"

"You're afraid you're not good enough. That Leonard will realize this one day, and it will all be over."

"Okay, I'm done talking to you, now." Penny shifted uncomfortably.

"Now, what I don't understand is where these thoughts come from? I'm sure Leonard has never given you any reason to feel this way."

"It's none of your business how I feel!"

"And yet," the Doctor continued, "you still believe he's better than you."

"He's a genius for god's sake! And I'm, I'm nothing. Just a waitress." Penny said.

The Doctor sternly looked at Penny. "No one is 'nothing', Penny. In fact, most people who believe they're insignificant turn out to be some of the most important people in history."

"Right," Penny said, unconvinced.

"I'm serious! Take Donna over there. She always believed she was just a temp, couldn't be anything more than that. But she managed to track me down, has traveled to dozens of planets, helped save most of them, been declared a god more than once, and most importantly has saved my life countless times. In more ways than she'll probably ever know," the Doctor added.

"But that's only in a television show!" Penny said. "None of that's real. At least, not for us."

"The point is, no one is 'nothing'. No one is insignificant. Do you know why he became friends with you? Why he wanted to keep seeing you after that first meeting? Because you were kind. Because you listened. Because you showed him a whole other world, and he realized he wanted more than just science and comic books. He wanted you. And it doesn't matter that you don't understand the laws of physics or know who Brent Spiner is, because he doesn't need that. He needs someone who can see things in a different way. Who can contradict him and question him and make him think about things he never would have considered before," the Doctor smiled. "And that, Penny, is what makes you so amazing, and why on one fall night in the future, you notice a pattern on the white board that no one else noticed. Not Raj. Not Leonard. Not even Sheldon saw it. But you did. They couldn't have done it without you, you know."

Penny was completely speechless after this speech. Her mouth hung open, stunned.

"And finito!" Howard suddenly proclaimed. "Done!"

"Brilliant!" the Doctor yelled, turning back to the group. Penny snapped her mouth shut and shook her head a little, trying to gather her racing thoughts. "Now let's just check the time lines one last time." The Doctor rushed over to the console and scanned the screen. "Perfect! The time lines are adjusting and re-arranging just like they should!" He looked at Donna. "Time for us to go, I think."

"Finally! These four are about ready to do my head in."

"Hey!" Howard exclaimed, taking offense.

"Look," Donna said, "I already have to put up with Alien Boy over there. I can't handle you lot on top of that!" She looked at Penny, "Seriously, I don't know how you do it all the time."

Penny shrugged. "Ah, they're not so bad." She caught Leonard's eye and winked. Leonard grinned.

"Right! Must be off, now." The Doctor bounced around to each of the five to shake their hands again. "It really was a huge honor to meet you. All of you." He glanced at Penny there. "Good luck with all your research! Hopefully, you'll never see me again except through the telly." He winked, and the guys laughed. The five called out their good-byes to the Doctor and Donna and started to exit the Tardis for the last time. Sheldon hesitated in the doorway and turned back to the Doctor.

"Well, it wasn't all I hoped it would be, but it was still a very pleasant encounter. Thank you, Doctor, for allowing me to work on your ship. I learned many interesting facts about Time Lord technology. Unfortunately, I anticipate some resistance when I attempt to share these facts in the online fanbase." Sheldon frowned.

"Well, that's fans for you," the Doctor replied. "Have a good life, Dr. Sheldon Cooper. Enjoy your Nobel Prize!"

Sheldon's face lit up. "Oh, I plan to!" And with that, he slipped out the door.

The Doctor turned to Donna. "So what do you think? Try for the Galigna Plains again?"

"Alright by me," she replied. "Just don't hit any more wounds in time!"

***~~***

The five of them stood around the living room and watched as the Tardis' gears grinded and faded away.

"Wow," Howard said after it was gone.

"The dematerialization sequence really does sound like that," Leonard said in awe.

"Yeah, too bad we won't remember any of this," Howard said.

"There is a slight chance that the time lines will bend around us, and you will remember everything," Sheldon replied.

"Wait, what do you mean 'you will remember everything'?" Leonard asked.

"I'm sure I'll remember no matter what happens next."

"No, no, no, Sheldon!" Howard protested. "Altered time lines is something not even your eidetic memory can overcome."

"Well, not on its own perhaps, but the eidetic memory coupled with my mental prowess practically guarantees I'll remember."

"Oh, really Sheldon?" Leonard asked, incredulously.

"Talk about an ego," Howard said. Raj nodded to show his agreement. Penny just rolled her eyes as the four guys continued to bicker over the likelihood of any of them actually remembering the day's events.

The time lines finished shifting and resolved the issue for them.

They never remembered any of it.


	10. Epilogue

**The Parallel Worlds Proof**

**AN:** The very last installment! This is a just a small scene that's supposed to take place sometime in December 2009 after the time lines have corrected themselves. It seemed like a good way to end the story. *winks*

**Epilogue:**

"So, I was thinking about the theory of multiverse the other day."

Leonard swallowed his food and looked at Raj. "What about it?"

"Well did you ever read Robert Heinlein's _The Number of the Beast_?"

"Oh, yes. The book postulated that devil's number was not actually 666, but (66)6 . I thought that was rather clever, but of course my mother was unimpressed. She declared the book must have really been written by the Devil and forbade me from ever reading it again," Sheldon said with a frown.

"Right, but the book also claimed that every time a fictional character was created, that character's world became a reality in another universe. And then book's protagonists were able to travel through all 6 dimensions of time to end up in different worlds. Like Oz."

"So, what's your point?" Howard asked.

"My point is, how cool would that be if our favorite fictional worlds existed as reality somewhere?" Raj said excitedly.

Leonard grinned. "Like somewhere in a parallel universe Admiral Adama leads the Battlestar Gactica in a war against the Cylons."

"Somewhere Superman sits up in his Fortress of Solitude," Howard said.

"And the Doctor wanders the universe in search of adventure," Sheldon added. All four guys stared off into space for a moment, enjoying the imaginary scenarios.

Howard suddenly broke out of it. "Hey, wait a second! These fictional characters don't realize that they're fiction because their world really exists. So that means _we_ could exist as fiction in another world."

Raj looked at him. "So like we're a television show in another universe?"

"Oh! Or a comic book! I hope we're a comic book," Sheldon said.

"Yeah!" The four guys grinned in silence for a few seconds.

"Wow, we really come up with some absurd ideas sometimes," Leonard said. The others murmured their agreement, and they all went back to eating dinner.


End file.
